This invention relates generally to the field of magnetic data storage devices, and more particularly, but not by way of limitation, to a method and apparatus for electrically interconnecting conductive traces on a printed circuit board assembly to an internal component housed within the head disc assembly.
Disc drives are used as primary data storage devices in modern computer systems and networks. A typical disc drive includes a head-disc assembly (HDA) and an attached printed circuit board assembly (PCBA). The HDA is an enclosed structure comprising a basedeck which supports one or more rigid magnetic storage discs that are journaled about a rotary hub of a spindle motor to form a disc stack. An array of read/write transducing heads are supported adjacent the disc stack by an actuator to transfer data via read/write circuitry provisioned on the PCBA to a host computer in which the disc drive is mounted. The PCBA includes a printed circuit board (PCB) upon which are mounted a plurality of electrical components. Modern PCBA""s make use of surface mount device technology in which electrical components are mounted to a single, xe2x80x9cprimaryxe2x80x9d side of the PCB without the need for through-hole insertion or two-sided manufacturing operations. The PCB also has a secondary side which, when mounted to the HDA, faces the basedeck.
Conventional actuators employ a voice coil motor to position the heads with respect to the disc surfaces. The heads are mounted via flexures at the ends of a plurality of arms which project radially outward from an actuator body. In addition to the read/write heads, the actuator assembly generally includes head wires, which conduct electrical signals from the read/write heads to a flex circuit that, in turn, conducts the electrical signals to a read/write channel located on the PCBA. Normally, the electrical signal paths are routed through one or more connectors en route to the read/write channel.
The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the heads move in a plane parallel with the surfaces of the discs. The pivotal movement of the actuator is controlled by selectively energizing the voice coil motor which operates in accordance with the well-known Lorentz relationship. Typically, servo circuitry located on the PCBA sends signals to the voice coil motor along the same flex assembly used to transfer read/write information to and from the heads.
The spindle motor comprises a brushless direct current (xe2x80x9cdcxe2x80x9d) motor having a stationary stator with a plurality of electrical phases, each phase having one or more sets of electrical windings that are wrapped around poles within the stator, with the sets of windings in each phase being electrically connected in series. The spindle motor includes a rotor mounted for rotation about the stator, with the rotor having a plurality of permanent magnets and an outer hub to which the discs are mounted. By selectively energizing the windings within each phase in the stator, magnetic fields are generated in the windings which interact with the magnetic fields of the rotor magnets, causing the discs to rotate in the desired direction at the desired speed. Typically, three or four signal wires are used to control the function of the spindle motor.
As mentioned above, both spindle motor and actuator circuitry are typically provisioned on the PCBA mounted to the underside of the HDA. Because it is necessary to maintain a sealed environment within the HDA, the connectors and signal paths between the PCBA and components within the HDA are designed to eliminate the exposure of internal components.
Traditionally, disc drive designers have used a three connector combination which includes a connector internal to the HDA, a pass through connector mounted adjacent the basedeck and a third connector mounted on the secondary side of the PCB. Under this scheme, the connector internal to the HDA is a fixed adapter that is attached to either the flex circuit assembly or the spindle motor. The pass through connector houses pins that mate with the internal connector within the HDA and pins that protrude through an aperture or slot in the basedeck. The third component, a free connector mounted on the secondary side of the PCB, receives the pins protruding from within the basedeck. U.S. Pat. No. 5,212,607 issued to Elsing et al. and assigned to the assignee of the present application provides a thorough discussion of a three-connector scheme.
Despite its simplistic function, the traditional three-connector scheme requires that a free adapter be placed on the secondary side of the PCB. With the availability of surface mount device technology, it has become cost inefficient to provision components on both surfaces of a PCB during manufacture. As such, it has become necessary to develop an effective means of providing communication between the HDA and the PCB without mounting components to both sides of the PCB.
One solution involves connecting a flex circuit to the internal component and feeding the flex circuit between the basedeck and the attached top cover. The flex circuit is then routed along the outside of the HDA and onto a connector mounted on the primary side of the PCB. An example of this approach is disclosed in U.S. Pat. No. 5,403,202 issued to Roehling. The disadvantage of this external feed approach is the exposure of the flex circuit to handling damage during the assembly process, customer installations and in automated production processes. The production difficulties arise when trying to locate, secure and connect the non-rigid flex circuit via automated means.
Another solution entails forming apertures in the basedeck and PCB and securing the internal component to the basedeck such that a portion of the internal component extends through the apertures in the basedeck and PCB. A connector mounted on the primary side of the PCB is then used to engage the exposed internal component. Such a design is disclosed in U.S. Pat. No. 5,705,868 issued to Cox et al. (xe2x80x9cCox ""868xe2x80x9d) which is commonly assigned with this application. Cox ""868 teaches a spindle motor that extends through the basedeck and PCB and a surface-mounted connector which engages the fixed pins of the spindle motor. Although Cox ""868 eliminates the need for mounting components to the secondary-side of the PCB, the connector is relatively complex and potentially expensive to manufacture.
Accordingly, there is a continued need for a cost-effective means for providing an electrical connection path between the PCBA and an internal component housed within the HDA.
The present invention is directed to an improved interconnection assembly for completing an electronic signal path between a printed circuit board assembly and an internal component within a head disc assembly of a disc drive. The printed circuit board assembly includes a printed circuit board which has a primary side suitable for mounting surface mount devices and a secondary side facing a basedeck of the disc drive.
The interconnection assembly comprises a conductive pin provisioned within a pin aperture in the printed circuit board and a fixed connector provisioned within a connector aperture in the basedeck. The pin is inserted and secured within the pin aperture using primary side assembly operations. A distal end of the conductive pin extends beyond the secondary side of the printed circuit board, thereby forming a secondary side electrical contact. The secondary side electrical contact is engaged with the connector while mounting the printed circuit board assembly to the head disc assembly.